THC percentage is a mass measurement
THC percentage states how much delta-9-tetrahydrocannabinol sits in a product by weight. Flower labeled 20% THC holds 200 mg of THC per gram. A vape cartridge labeled 80% holds 800 mg per gram. The number is a concentration, not a dose. Dose equals percentage multiplied by the weight consumed.
cannabis thc percentage explanation
Total THC versus delta-9 THC
Fresh cannabis holds most of its THC as THCA, the acid form. Heat removes a carboxyl group and converts THCA into THC. Labs report both figures. Total THC = delta-9-THC + (THCA x 0.877). The 0.877 factor accounts for the CO2 mass lost in decarboxylation. THCA has a molar mass of 358.5 g/mol. THC has a molar mass of 314.5 g/mol.
Cannabis THC Percent for Pain: How Much Do You Need?
Typical ranges in US retail products
- Flower: 15% to 25% THC.
- Pre-rolls: 15% to 25%, same as the flower inside them.
- Concentrates: 60% to 90%.
- Vape cartridges: 70% to 90%.
- Edibles: labeled in mg per serving, not percent. The standard single serving in regulated US states is 10 mg.
What the number does not tell you
Percent THC says nothing about other cannabinoids, terpenes, pesticides, mold, or heavy metals. It does not predict the effect for one person. Inhaled bioavailability runs from about 10% to 30%, and depends on inhale depth, hold time, and device temperature. Oral THC passes through the liver and converts to 11-hydroxy-THC. Onset for edibles is 30 to 60 minutes. Effects can last 2 to 4 hours.
Tolerance shifts the response. Daily users report smaller effects at the same dose. Lab accuracy also varies. State-required tests use different methods, and split-sample comparisons have shown gaps of several percentage points between labs on the same material.
How to turn percent into dose
Multiply percentage by weight to get milligrams. One gram of 20% flower is 200 mg THC. A 0.5 g joint at 20% is 100 mg THC. A person who inhales one third of that joint takes in about 33 mg. Start low. Raise the amount in small steps across separate sessions.
Where convenience fits
Pre-rolls, vape pens, and single-serve edibles remove the step of weighing flower and calculating dose. That convenience does not change the math. The label still gives a percentage or a milligram count. Read it before you use the product.